proposal: tests: introduces Espresso for integration tests

For quality improvements, and to avoid regressions, the client should
have automatized tests to validate transitions, contents and scenarios.
This patch introduces two examples of tests working with Espresso, which
is integrated with Android Studio.

Some notes:
+ "pm clear" is not executed between all tests, so all the tests should
be considered as one test-suite. If we want to make all the tests
completely independant, the TestOrchester should execute a "pm clear"
between two test. Also because of this, Test are ordered via
Testxxxx.
+ To generate tests the easy way can be:
    + Disable animations on the host device
    + In Android studio, Run, Record Espresso Test
+ Sometimes, elements take time to be shown. In this case, the test
must be completed with waiting events. waitUntilViewIsDisplayed()
can be used for this.

Change-Id: Ie44b2568fb9c8570978d1d1af94562bccba6b6b2